Depth-to-Water Maps to Identify Soil Areas That Are Potentially Sensitive to Logging Disturbance: Initial Evaluations in the Mediterranean Forest Context

Abstract

Scientific research on reduced-impact logging has been addressed to develop effective approaches and methodologies to limit soil disturbance caused by forest operations. In recent years, the development of soil trafficability maps based on soil wetness indices is the approach that has been extensively used in the context of the Boreal forests. In particular, the depth-to-water (DTW) index has been identified as an interesting solution for the identification of areas particularly sensitive to soil disturbance. This study aimed to evaluate the cost-benefit factor of DTW maps for the identification of soil-sensitive areas in the Mediterranean context. In particular, a DTW map was developed for two oak coppice areas located in Italy and harvested over a period of 2–4 years with different mechanisation levels. Soil surveys concerning soil moisture, physico-chemical properties (bulk density, penetration resistance, shear resistance, organic matter), and biological properties (soil microarthropods community measure via soil biological quality (QBS-ar) index) were carried out in these forests, checking for significant differences between the zones at DTW index ≤1 (which should be more sensitive to soil disturbance) and the other areas of the forest soil. The results obtained revealed the efficiency of a DTW index in potential areas at a higher level of soil moisture. On the other hand, the values of soil physico-chemical properties in the areas at a DTW index ≤1 did not differ significantly from the ones in other zones. However, the values of the QBS-ar index in areas with a low DTW index were significantly lower than the ones in zones at the DTW index >1. Therefore, the obtained findings reveal that the DTW index is a reliable tool to identify and predict which areas are more prone to impact soil biological properties.